I would suggest in the beginning take him out, take him out and take him out somemore

He is just a bitty baby and has no idea where the heck he is supposed to do his business...never mind he should be alerting you to do his business. Potty training can be a very frustrating thing...we've just about turned the corner with Trudy, although I am not going to claim success just yet...
But think of it this the dog has to learn lots of things relating to where to do his business, first he has to realize the sensation of "oh I have to go" then he must hold it, alert you and go outside.
I would suggest that you take the reins and just keep taking him out and praising him when he does his business...also when you bring him out let him pee/poop whatever necessary and then right back in the house for now you want to associated going outside with going the bathroom only....not playtime or what have you...
As for at night, i set my alarm and brought Trudy out every 2 - 3 hours in the beginning, she makes it through the night now 98% of the time she is almost 5 months old....
And the last reason i would not wait until you get an "i need to go out" cue from your dog, is sometimes you won't get one...that was our problem, she knew she was to do her business outside, she just didn't know how to TELL me she had to go out. So now we have a bell on the door and she rings it when she wants to go outside, but that's a whole new thread!! Good Luck with Bear and keep us posted!